The present invention relates to packages having caking preventing function which is suitable for use for powders or granules having caking property by the effect of water and containing a very small amount of water.
Among amino acids, threonine, arginine hydrochloride, lysine hydrochloride etc. cake easily. Even when these amino acids are packed in a plastic bag for storage, in extreme cases they may cake so that the total contents become as hard as stone. Therefore, extreme care has been taken to prevent them from caking.
Hitherto, there has been employed a double packing bag wherein both an inner and an outer bags have no or extremely low water vapor permeability and desiccants such as silica gel and the like are placed between the inner and outer bags in order to prevent completely the entry of moisture into the packaged article from the outside. However, even though packed in such double bag, the total contents in the inner bags may cake and form hard lumps while in storage for a long-term over one year. In some cases, the contents cake in several months' storage.
As the caking inhibiting means for L-lysine hydrochloride, a process was developed for changing L-Lysine hydrochloride dihydrate into .alpha.-form crystals of anhydrous, L-Lysine hydrochloride at a temperature of 115.degree. C. or higher and then packaging in a bag as disclosed in Japanese KOKAI Publication No. 45145/1982. However, this process is not widely applicable as the caking preventing means but a particular improvement in the caking property of L-lysine hydrochloride alone.
In addition to amino acids, inorganic salts such as ammonium nitrate and the like have encountered the similar caking problem. The improvements were to coat the particle surface with wax or other surface covering agent. In this process, however, the lowering in the purity of the products is unavoidable.
Furthermore, in order to prevent the caking of powders or granules of hygroscopic food products during the preservation, desiccants such as silica gel etc. have directly been placed with articles in the container. However, this process has a disadvantage that the packaged articles suffers a danger of contamination with the drying agents of desiccants. Therefore, it is not suitable for the package of pharmaceuticals in bulk and of the raw materials for manufacturing pharmaceuticals such as amino acids for transfusion which high purity is required.